It is well known in motor vehicles to provide an air bag assembly for protection of a vehicle occupant. The air bag assembly typically includes an air bag module located beneath the surface of the instrument panel.
Air bag modules have been developed for assembly in a modular form. A common type of air bag module includes an inflator, a housing for holding the inflator and including an air bag deployment opening, and an air bag normally stored in a folded condition within the housing near the housing opening. The housing is normally made of sheet metal and, during vehicle assembly, the entire module is attached via the housing to the instrument panel support structure located beneath a cover door formed in or mounted on the upper or rearward surface of the instrument panel in front of the passenger seat.
The cushion is normally positioned atop the inflator near the opening in the housing, so that, upon the vehicle experiencing a predetermined rate of change in velocity, the inflator discharges gas to inflate the air bag for deployment through the opening and for forcibly opening the cover door.
As an alternative to these modules, some vehicles are designed to incorporate the housing as an integral part of the instrument panel support structure. This enables the use of a simplified air bag module which does not include the housing. Such a simplified module in current use is known as a "soft-pack" module and typically comprises an inflator, an inflator retainer for supporting the inflator, and an air bag which lies atop the inflator and is held in place by an air bag retainer.
The prior art includes some simplified modules in which the inflator is operatively connected by the inflator retainer to the housing adjacent a bottom housing opening. In other modules, the inflator is directly connected to the housing by insertion through a side opening included in the housing. These arrangements require that manufacturing operations be performed on the housing to provide either a side opening or a bottom opening to accommodate connection of the inflator to the housing. Access to perform these manufacturing operations can be difficult when the housing is provided as an integral part of the instrument panel support structure. In addition, assembly of the inflator to the integral housing via a side or bottom opening may be difficult due to limited access underneath the instrument support structure.
The prior art also includes other simplified air bag modules in which the entire module, including the inflator, is capable of unidirectional insertion into the housing via the housing opening. Thus, the same housing opening which is easily accessible during vehicle assembly is used for both module installation and air bag deployment. Therefore, additional manufacturing operations typically performed on the housing to provide insertion access or support for the inflator are eliminated.
It is typical in existing simplified air bag modules, to have the air bag located atop the inflator. However, this arrangement may permit some discharging inflator gas directed towards the air bag to leak out through the housing opening into ambient air, thus reducing the inflator gas available for air bag inflation.
Furthermore, the simplified modules typically include an inflator retainer made of stamped, cast or machined metal and having a complex shape resulting in increased manufacturing costs for the air bag module. These inflator retainers also typically have substantial structure which adds weight to the air bag module.
Thus, it would be desirable to provide an improved simplified air bag module which has reduced mass, which is simple and inexpensive to manufacture, and which maximizes the utilization of inflator gas for air bag inflation.